How do you produce an echo?

Imagine a pool of water. If you dropped a rock in the water you would cause ripples that would travel out evenly in all directions. When one of those ripples hits a wall, you can see that the ripple bounces off the wall. Sound works the same way. Sound is basically just ripples in the air (vibrations). When a sound vibration hits a wall it bounces back much like the ripples in water.

* When you hit something and waves travel through the air to your ears. Sometimes sound reflects again.